Infrared oven



April 17, 1951 w. J. MISKELLA INFRARED OVEN Filed Nov. 30, 1945 '4 WW mw w my w w NM Patented Apr. 17, 1 951 UNITED STATES PATENT OFFICEINFRARED OVEN William J -Miskella, Cleveland, Ohio Application November30, 1945, Serial No. 632,059

1' Claim. 1

My invention relates to heating and drying equipment, and particularlyto an infrared oven through which the objects to be subjected toinfrared radiation may be passed by means of a conveyor system.

In spray coating objects with many types of commercial coatingvmaterials, such as lacquers and enamels and particularly the cheapergrades of these paint-like substances, a large amount of a very volatileand inexpensive solventis used as a thinner which must be removed duringthe baking and drying step of the coating process. In recent years therehas been an increase in the use of infrared radiated heat for baking anddrying coating materials, and it has been found that it is necessary todevote considerable time to the maintenance of the equipment,particularly when cheap materials are used. As the object is passedthrough the infrared oven and: the volatile constituents of the solventare removed through the application of. infrared radiated: heat, a fogof this solvent will accumulate in the oven, and because of its somewhatgummy characteristics, it will adhere to parts of the oven such as theinfrared lamps and the reflective surfaces. In order to preserve theefficiency of the oven, the infrared lamps must be cleaned frequentlyand the reflective surfaces polished, else there be too great a lossthrough the absorption of heat by this gummy condensation on thesurfaces of the'oven parts.

It has been the practice to attempt to remove the evaporated solventsbypassing a stream of air lengthwise through the oven; thatiis, parallelto the movement of the object being treated and substantially orgenerally perpendicular to the path of heat radiated from the infraredlamps.

This method of air circulation has been found objectionable because thedensity of the fog of evaporated solvent is cumulatively concentratedtoward the air outlet end of the oven. The cumulative movement does noteffectively prevent it from condensing on such parts to an extent whichis objectionable, and there is necessity for constant maintenance of theoven to keep it clean. 7

Another object to the endwise flow of air through the oven is that ithas the effect very rapidly of removing the air which may become heatedby contact with the infrared bulbs and the objects being heated, andsuch removal is an undesirable heat loss from the oven.

It is therefore the principal object of the present invention to providean infrared oven which overcomes the objections now present in manycommercial ovensas outlined hereinbefore.

It is. another object to remove the fog of evaporated solvent fromtheoven in such a manner that the fog does not tend to concentrate at anyparticular spot in the oven.

Another object is to remove the fumes from the evaporation of thesolvent from a coating material in such manner that there is nointerference with the transmission of the infrared radiated heat fromthe infrared lamps to the'objec Another object is to. provide aninfrared oven in which the lamps and reflective surfaces of the oven aremaintained in a substantially clean condition during normal operation ofthe oven.

A further object is'to provide an infrared oven in which a minimumamount of maintenance is required.

It is a further object to provide an infrared oven in which the air iscirculated in such a manner as to effect a cooling of the infrared lampsand the transfer of heat by conduction and convection from the lamps tothe object being heated.

It is another object to provide an infrared oven having objects andadvantages claimed herein which is inexpensive in construction andefficient in operation.

Other objects and advantages will become apparent from the followingdescription 'taken in conjunction with the drawing which contains asingle figure illustrating one embodiment of my invention.

My novel oven includes a pair of heat insulated, substantially parallelwalls ill and I2 which may be supported upon a frame. which has not beenshown for the purpose of simplicity of illustration. At their upper endsthe space between the walls is closed by a support l t for the infraredlamps which may be of the type illustrated, described, and claimed in myco-pending application Serial No. 632,058, filed November 30, 1945, nowPatent No. 2,478,001. The space between the lower ends of the walls isclosed by an opensided duct [6 which will be more fully describedhereinafter.

Each of the walls l0, [2 may be constructed so that their inner surfacesi8 are coated with a reflective material such as porcelain, or chromiumor cadmium plating for instance. The space between the inner and outersheets forming the walls Ill and I2 is filled with asbestos, Fiberglasor other suitable insulating material 20. The walls Ill and 12 areformed in a box-like structure and support the means H for holding thebank of lamps in position.

The support l4 comprises a number of box-like elements 22, each of whichis perforated at 24 to permit the insertion of the base of the infraredlamp 26 into a standard socket 28. The socket 28 is mounted on a flangedU-shaped strap 30 which is bolted to the bottom 32 of the box 22. Theboxes are supported on the upper edges 34 of the walls In and I2 bymeans of small spacer chairs 36 which may be welded or bolted to theside walls of the boxes 22. Depending from the bottom 32 of the box 22is a heat insulated reflective panel 38 of the type described in myaforesaid co-pending application. The panels 38 close the space betweenthe upper edges of the walls I0, 12 and are provided with openings E6 topermit insertion of the necks and bases of the infrared lamps 26.

At the bottom of the oven the duct [6 preferably runs its entire length,or if the oven be exceedingly long, a number of such ducts may be placedlengthwise of the oven. These ducts are attached to the bottoms of thewalls Ill, I2 by means of flanges 40 which may be welded or boltedthereto. The duct [6 has generally sloping side walls 42 which inclinetoward a bottom wall 44. Approximately at the mid point of each duct 15,there is a large opening 46 which leads to a duct 48 forming the inletfor a blower 50 having an exhaust 52. The blower 50 may be of anystandard construction and of a size suitable for creating a proper draftof air through the oven and may be driven by an electric motor, notshown.

Adjacent the bottom of the oven and extending between the walls and I2is a heat insulated perforated panel 54 which rests upon rails 56 whichare welded or bolted to the inner sides of the walls IE], [2. The panel54 is composed of a bottom sheet 58 having a regular pattern ofperforations 6!] and a top sheet 62 which contains perforateddepressions 54 coinciding with the perforations B0 in the sheet 58. Thetop sheet 52 is bent down at the edges to provide depending flanges 66which ride on the rails 56, permitting the heat insulated panel 54 to beslid lengthwise of the oven, making it easily removable for cleaningwhen necessary. Suitable heat insulation material is retained betweenthe sheets 58 and 62. If desired the panel 54 may be made in sections tofacilitate handling during removal.

Between the bank of lamps 26 and the heat insulated panel 54 is aperforated or screen conveyor 68 which is supported on rollers 70journaled in the walls IO and [2. The ends of the oven are closed bysuitable panels (not shown in the drawing) which have openings in themof such size as to permit passage of the objects being treated, which,in the illustration, are dishes 92. These end closing panels may or maynot be heat insulated, as conditions dictate. It is understood, ofcourse, that other types of conveyor systems may be used depending uponthe size, shape and other characteristics of the objects being treated.

The operation of this infrared oven is relatively simple and entailsmerely insuring that the blower speed is sufficient to create a propercirculation of air through the oven so as to remove the fumes or fog ofevaporated solvent. When the oven is operating properly, the conveyormeans carries the objects through the Oven directly in the path of theheat radiated from the infrared lamps 26. The air circulated by theblower 5D enters the oven through the space 14 between the boxes 22 andthe insulated panel 38, and then passes down through the openings 16 inthe panel 38. As the air passes over the lamps 26, it becomes heated andin turn cools the lamps and their bases which is desirable because thetemperature of the lamps is thus maintained at a level which is lowenough to prevent deterioration of the cement which secures the glassenvelope in the metal base, thereby increasing the effective life of theinfrared lamps. The heated air passes down through the oven between thewalls In and I2 and over the objects which are being subjected toinfrared radiation. The path of circulated air is substantially parallelto the direction of the rays radiated from the infrared lamps 26. Thusthe tendency of the evaporated solvent to rise in the oven and condenseon the surface of the bulb or on the reflective surfaces of the walls I0and I2 is inhibited. Furthermore, because the air which passes over thelamps 26 becomes heated, it can transfer a substantial portion of thatheat to the object, thereby increasing the efficiency of the oven.

The conveyor system-illustrated as a belt 68- is so constructed that itdoes not present an obstacle to the relatively free flow of airtherethrough or therepast. By the time the air reaches the panel 54, itcontains a substantial amount of evaporated solvent and a portion ofthis gathers or accumulates on the top surface 62 of the panel 54. Theair is drawn through the panel 54 into the duct [6 and is exhausted bythe blower through the duct 52 to the atmosphere or to some othersuitable place where the volatile solvents will not create a nuisance.

It has been pointed out that the air which is circulated through theoven carries an appreciable amount of evaporated solvent which condenseson the top surface of the panel 54; after a time it will becomedesirable to remove this gum or crust. For this reason, the panel 54 ismounted on the rails 56 which permit the panel or sections thereof to beslid lengthwise of the oven and removed. It may be wiped off with acloth and a suitable cleaning solvent such as benzine, carbontetrachloride, or naphtha. Periodically, it may be found desirable toclean the inner surface of the duct l6; however, this is not essentialbecause once the air has carried the solvent past the conveyor, anyaccumulation of evaporated solvent on the surfaces of the lower portionof the oven or on the panel 54 is not material or harmful and in no wayaffects the efflciency of the oven or its operation.

Having described the preferred embodiments of my invention, numerouschanges in its construction and operation may become apparent to thoseskilled in the art and may be made without departing from the spirit andscope of my invention, and I therefore desire to be limited only by thescope of the appended claim.

I claim:

An infrared oven adapted to have a conveyor pass therethrough to carryobjects to be subjected to infrared radiation comprising in combinationa pair of substantially parallel walls, a plurality of infrared lamps, alamp support bridging between the upper edges of said walls but spacedtherefrom to provide an air inlet, said lamps depending from saidsupport and into the space between said walls, a heat insulatedreflective panel carried by but spaced from said lamp support closingthe space between said walls adjacent the top thereof, said panel havinga plurality of lamp openings through which said infrared lamps projectinto the space between said walls, the space between said lamp supportand said panel and said lamp openings forming an air inlet passage, anair outlet duct closing the space between said walls opposite said bankof infrared lamps, said duct having an opening communicating with theinterior of the oven, and an air circulating means for causing flow ofair through said inlet passage, between said walls over the objectsbeing subjected to infrared radiation and out through said duct.

WILLIAM J. MISKELLA.

6 REFERENCES CITED The following references are of record in the fileofthis patent:

UNITED STATES PATENTS Number Name Date 1,006,767 Manger Oct. 24, 19112,113,770 Richardson Apr. 12, 1938 2,325,050 Goodwin et al July 27, 19422,347,407 Goodwin et a1 Apr. 25, 1944 2,360,257 Muller et a1. Oct. 10,1944 2,387,804 Miskella Oct. 30, 1945 2,389,586 Andrews Nov. 27, 1945

